1. Field of the Invention
The present invention relates to a power steering system for use in a large vehicle which is of the speed-responsive and load-responsive type.
2. Description of the Prior Art
In this type of large vehicle, i.e., a vehicle in which the weight of a steering axle is especially large, the construction of the power steering system is such that a hydraulic pump and a power cylinder need to be large in order to secure stationary swing capability at the time when the vehicle is at a standstill as well as the steering power required during extremely low-speed running of the vehicle.
On the other hand, however, this means that the load imposed on the engine when the hydraulic pump is driven becomes extremely large, and a large load is applied to the engine even during high-speed running when the hydraulic pump is not required to exhibit a large supplying capability for the hydraulic pump. Thus, the power consumption efficiency has tended to be low.